Either $callback or $id_base can be used
$id_base is the first argument when extending WP_Widget class
Without the optional $widget_id parameter, returns the ID of the first sidebar
in which the first instance of the widget with the given callback or $id_base is found.
With the $widget_id parameter, returns the ID of the sidebar where
the widget with that callback/$id_base AND that ID is found.

NOTE: $widget_id and $id_base are the same for single widgets. To be effective
this function has to run after widgets have initialized, at action {@see 'init'} or later.